A packing of the aforementioned type is already known from the German Auslegeschrift No. 1,776,210. The packing is composed of thin layers of a non-metallic working material, in particular plastic. The corrugations or folds of adjacent layers are joined together at their intersection points by adhesive or welding to produce a uniform body. To increase the mechanical strength of the packing, it is known from the German Ausgeleschrift No. 1,776,210 to provide the two longitudinal sides of the layers with a reinforcing edge which has a greater mechanical strength than the inner portions of the layers. In the finished packing one longitudinal edge forms the lower edge of the packing. The reinforced edge should contribute to increasing the mechanical strength of the packing against external loads and also to the stability of shape of the folds. It has been shown that inspite of the improved construction, a secure position of the packing on the supporting points is not guaranteed in particular with temperature loads over a long period of time, which can at times exceed the specified operating temperature. Tests have been made to meet these difficulties by increasing the temperature stability of the plastic. This can involve considerable additional costs.
Further, the German Auslegeschrift No. 22,34,013 proposes to fold over the edge of the plastic layer before corrugations or folds are formed in order to produce a reinforced longitudinal edge in a plastic foil packing. This packing therefore has a longitudinal edge reinforced by folding having corrugations or folds.